Add comprehensive environments table to main README

- Added new "Available Environments" section after Featured Example
- Table includes 10 environments with domain, description, and links
- Organized by purpose: testing, code execution, LLM training, games, dev tools, finance, traffic, safety
- All links verified to point to correct environment READMEs

Co-authored-by: init27 <[email protected]>

Author: Copilot

README.md

@@ -10,6 +10,25 @@ An e2e framework for creating, deploying and using isolated execution environmen
 
 **🚀 Featured Example:** Train LLMs to play BlackJack using [torchforge](https://github.com/meta-pytorch/torchforge) (PyTorch's agentic RL framework): [`examples/grpo_blackjack/`](examples/grpo_blackjack/)
 
+## Available Environments
+
+OpenEnv provides a growing collection of environments across different domains for agentic RL research:
+
+| Environment | Domain | Description | Documentation |
+|-------------|--------|-------------|---------------|
+| **Echo Env** | Testing | Simple message echo for testing framework infrastructure | [`src/envs/echo_env/`](src/envs/echo_env/README.md) |
+| **Coding Env** | Code Execution | Execute Python code in sandboxed environment with smolagents | [`src/envs/coding_env/`](src/envs/coding_env/README.md) |
+| **Chat Env** | LLM Training | Chat-based environment with tokenization and message history for conversation RL | [`src/envs/chat_env/`](src/envs/chat_env/README.md) |
+| **Atari Env** | Classic Games | 100+ Atari 2600 games via Arcade Learning Environment (Pong, Breakout, Space Invaders, etc.) | [`src/envs/atari_env/`](src/envs/atari_env/README.md) |
+| **OpenSpiel Env** | Game Theory | 70+ games from DeepMind's OpenSpiel (Tic-Tac-Toe, Poker, Chess, Catch, 2048, etc.) | [`src/envs/openspiel_env/`](src/envs/openspiel_env/README.md) |
+| **Git Env** | Software Dev | Git repository operations via Gitea for software development tasks | [`src/envs/git_env/`](src/envs/git_env/README.md) |
+| **FinRL Env** | Finance | Stock trading environment with technical indicators and portfolio management | [`src/envs/finrl_env/`](src/envs/finrl_env/README.md) |
+| **SUMO-RL Env** | Traffic Control | Traffic signal optimization using SUMO microscopic traffic simulation | [`src/envs/sumo_rl_env/`](src/envs/sumo_rl_env/README.md) |
+| **TextArena Env** | Word Games | Word games and reasoning tasks (Wordle, GuessTheNumber, etc.) | [`src/envs/textarena_env/`](src/envs/textarena_env/README.md) |
+| **DIPG Safety Env** | AI Safety | Medical domain safety training for high-stakes LLM applications with hallucination detection | [`src/envs/dipg_safety_env/`](src/envs/dipg_safety_env/README.md) |
+
+Each environment follows the standard OpenEnv API (`reset()`, `step()`, `state()`) and can be deployed via Docker containers for isolated execution.
+
 ## OpenEnv on partner platforms:
 
 - [Lightning AI Studio](https://lightning.ai/environments?section=featured)